I have 4 20 inch C1s and have used 3 Tethrd Ones at our Michigan meet-up last May.
Overall
I love my C1s and if I had to buy sticks again this is likely where I would end up. I'm 5' 10" and 265, there is certainly some flex in the steps, but after talking with TN and reading the 3rd party report I'm confident in them. I will note these are Gen 2 sticks and those did address the squeaking issue, even being my size, I've not heard them squeak once. TN has a 3-year warranty and Tethrd has 1 year. Honestly though, I think both companies would take care of you as best they could even outside of the warranty. I've not used TNs warranty but have used Tethrd's once for a platform and they shipped me a new one no questions asked and included a label in the box to return the old one.
Aiders
I'm not as sold on the cable aiders as I want to be in the TNs. They hang a little close to the tree and sometimes it's a pain, especially in my lacrosse rubber boots to get my foot in them. I am considering dropping the cable aiders from 3 of them, and just running it on the bottom stick. If you used a standard amsteel aider I think you would be fine on either stick, but you lose some of sleekness of the cable aiders.
Weight
While the TNs are light, I didn't think they had that same WOW factor as when you pick them up compared to the One. With the cable aider and daisy chain, I think they come out to 1.51 on my scale. Light for sure, but not 15.9 ounces. It is much closer if you pull the cable aider out of the TN, then it's 1.2 vs .98. On the flip side the extra weight does get you a little more, the TNs have an extra 1" per step which might matter to those would are counting inches
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Attachment Method
As far as attachment methods I still like using a trucker hitch around a button with my daisy chains. It's rock solid, quick and you get nearly 0 stick sag. Since I don't own the One's I only got to use the unique attachment method a half dozen times. I was slow and clunky with it, but if you owned them I'm sure you would get really quick with it and eventually be faster than the trucker hitch. I don't recall how much stick sag there was with them.
Noise
The C1s are QUIET out of the box, with no modification there likely is no other stick that compares. If you don't want to do a ton, or any, extra work to your sticks to silence them these are where you need to go. I have 2 tiny .5 x 1-inch pieces of stealth strips on each where the stick rests when stacked against the standoff, that's it. If you do bump the sticks together it's very much a quiet thud, and it's true if you bump the steps and standoffs it sounds like rattling antlers.
Bone stock the One sticks are LOUD, high pitched ting when bumped together and it almost echos. From the videos I've seen and talked with folks significant improvements are made when you stealth strip and foam the tubes, but there is a decent cost and time associated with that.
Foot Room
People always talk about foot room on trees, and yeah there is a definate difference between EWO and everyone else, honestly though, unless it's a 1 stick with a platform on top I think foot clearence to the tree is overrated. How long are you standing on that stick when you're climbing up with multiples, 1 maybe 2 minutes tops? Just stand duck footed and be done with it. I didn't have issues with either of these sticks.
Conclusion
I've tried a lot of sticks, not as many as some out there, but a decent amount. I think that when the newer variation of the One's come out, if everything lines up as they claim it will, these will be two of the best, if not the two best, stick sets on the market.
